Description

Encephalartos paucidentatus.

RSA Tree No. 11.

Family:Zamiaceae. This family of perennial cycads has 8 genera and about 200 species. They are only superficially palm or fern like. The cycad tap Root is soon replaced by lateral roots, which become woody. Cycads have coralloid roots that contain symbiotic cyanobacteria (blue-green algae) that fix atmospheric nitrogen in association with root tissue and produce important amino acids for the plant. Stems are cylindrical and southern African species do not have persistent leaf bases. All are evergreen with pinnately compound Leaves. The Leaflets have parallel (or nearly so) veins. 2019.07.15

Name derivation: Encephalartos – within-head-bread: referring to the starchy bread that can be made from the pith of the inner trunk. paucidentatus –few teeth – referring to the leaflets.

The genus Encephalartos includes some of the most primitive living Gymnosperms. Unlike other members of the family Zamiaceae, species in the genus Encephalartos have leaflets that lack a central Midrib (vein). Diamond shaped leaf scars remain on the trunk. The hard prickly leaflets do not bend easily. The sunken leaf veins are parallel or almost so. Stomata (structure utilising 2 guard cells, which unlike lenticels, can control the gaseous exchange) are present on the lower surface and may occur above. All species are dioecious with male and female Cones on separate plants. These cones develop in the centre of the leaf whorls. At maturity, the Seeds are released when the Female cones disintegrate. All species produce poisonous glycosides (cycasins). The African plants in the genus Encephalartos include about 66 species and there are about 30 species are in southern Africa.

Tree

The palm-like, woody Tree has a trunk is up to 7m high. It has a large pith. The tree and leaves have a spread of up to 5m. The stems may grow along the ground without establishing roots. The trunk is straight but may be reclining. It is up to 70cm wide. Branches do arise at or near the base. Additional stems may arise from suckers at the base.

Photo: David becking.

Leaves

Cycads are unique Gymnosperms with compound leaves. On this evergreen tree the Leaves are pinnately compound (leaflets arranged along either side of the leaf rachis – central stalk). Leaves are persistent – lasting more than a year. The Crown has straight or slightly curved leaves with each longer than 1,2m and up to 2,5m in length. Plants that are growing in shade tend to have longer leaves. The spread of the leaves is about 5m. Brown woolly hairs cover the centre of the crown. Leaflets are broad, straight or slightly sickle shaped. Central leaflets are up to 3,2cm wide. The leaflet apex tapers. Leaflets point upwards at the end of the leaf and those further away bend downwards. Twenty or more distinctly parallel raised veins are visible below. Petioles (leaf stalks) are initially green but become yellow. Petiolules (leaflet stalks) are absent. The under surface of a leaflet and the leaf stalk may be hairy – especially when young. There are few or no prickles. When present, prickles occur on either side of the leaflet margins. Leaflets close to the leaf base are reduced to prickles. Leaf bases remaining on the tree for a while after the leaves have fallen.

Photo: David Becking.

Photo: David Becking.

Cones

The tree is Dioecious (having male and female cones on separate plants). Up to 5 Male cones are formed which produce motile sperm. Each cone is up to 60cm long and is covered with brown hairs. These cones are perched on a 10cm long stalk. Up to 5 large, golden yellow Female cones may be formed – each up to 50 x 25cm. They are hairy when young and produce naked ovules. Wind or insects (possibly snout beetles) pollinate them. The cones rest in a short stalk. The red Seeds are about 4 x 2,5cm.

Gymnosperms have unenclosed or naked seeds. They have no flowers or fruit and the seeds are often contained in cones. In the Angiosperms (flowering plants), the seeds are enclosed in an ovary. In the Gymnosperms, there are 2 modes of fertilization. In all the Cycads (including Encephalartos) and the single extant (not extinct) species of Ginkgo (Ginkgo biloba), the male cones produce motile sperms. The remaining members of the Gymnosperms all have non-motile sperm with no flagella and are moved along with a Pollen tube to the egg.

Distribution & Ecology

These Trees occur in the mountains of eastern Mpumalanga and in North West Swaziland. They are located on mountain slopes – between 1 000 and 1 700m. Birds, monkeys and baboons collect the Fruit. After they consume the outer covering, these animals discard the seeds, thus dispersing them.

Ethnobotany

This is a popular, now threatened cycad. A permit required for having one. These cycads require quite a lot of space. They are faster growing than most cycads and should be planted in frost-free areas and watered regularly. Choose the spot carefully because they do not relocate well.